CLINICAL-PERFORMANCES OF 3 CREATINE-KINASE MB MASS ASSAYS FOR EARLY DIAGNOSIS OF MYOCARDIAL-INFARCTION - COMPARISON WITH MB ISOENZYME ACTIVITY

In 98 patients consecutively admitted in a medical intensive care unit, an aliquot taken from the blood sample withdrawn for the cardiac enzyme admission request has been frozen. After thawing of these 98 aliquots total CK and the creatine kinase MB isoenzyme were measured on the same day. For this last determination, four methods were used and compared: an immunoinhibition method (Merck) and three immunoenzymatic assays (Abbott on IMX; Baxter on Stratus II; Hybritech on single use Icon cylinder). In 19 out of the 98 patients studied the diagnosis of myocardial infarction was made retrospectively by a cardiologist. This diagnosis was established according to the criteria defined by the WHO. The clinical performances (sensitivity, specificity, positive predictive value, negative predictive value) have been calculated for each test according to the following criteria: on the one hand, a cut-off of 8% (reference range of our laboratory) for the immunoinhibition technique; on the other hand, a cut-off defined by the manufacturer together with a cut-off obtained from the ROC curves for the three immunoenzymatic assays. Our results clearly demonstrate that the clinical performances of the three immunoenzymatic CKMB assays are very comparable and appear to be much better than the immunoinhibition method which should be abandoned.